When installing gas turbine units having a power generating capacity below 60 megawatts, the whole gas turbine can be transported and erected as a unit which has already been assembled in the factory. Such a method is not feasible, however, for apparatus whose generating capacity is in excess of 60 megawatts since, with such larger apparatus, the gas turbine is generally delivered to the installation site as two separate units comprising a gas generator unit with a combustion chamber as one unit and also a separate power turbine unit.
With such higher capacity apparatus, the gas generator is provided with a shaft which must then be appropriately coupled with a mating bearing in the power turbine unit. Incidentally, the reason that the bearing is preferably included as a part of the power turbine unit is to have the bearing at as great a distance from the combustion chamber as possible so as to avoid harmful heating of the bearing.
The fact that the shaft pivot of the gas generator during the installation in the machinery hall of the power station must be inserted into a bearing arranged in the power turbine unit, complicates the connection of the two units to a high degree. In the case of an undivided gas turbine, only two large components need be connected together, namely the gas turbine and the generator, and this is made by means of a flange connection. In the installation of the latter type apparatus, if the connected halves are not fitted together sufficiently well at the first attempt of adjusting, no harm is done. Even if the connected halves are in contact with each other it is possible to adjust them vertically and laterally relative to each other. However, in connecting the above-mentioned gas turbine units, i.e. the gas generator and power turbine, which may each weigh more than 70 tons, for example, any excessive misalignment when joining the two parts may cause severely detrimental scraping of the bearing material even before the seizure is noted.
It has been found that the above-mentioned joining of the two units may be performed with good precision if the gas generator is allowed to hand freely in space from a suitable travelling crane. It is then possible, when the units are suitably coaxially aligned, to insert the tip of the somewhat bevelled shaft pivot into the outermost end of the bearing. Adjustments in lateral and vertical direction may then be performed with the help of the travelling crane. However, such a procedure, in which a travelling crane takes up the full weight of the gas generator, although readily applicable when assembling the gas turbine in the workshop where the manufacture takes place, is not necessarily feasible when installing the turbine in a power station. Thus, to be dependent on such a procedure when the gas turbine is mounted in the power station requires that the machinery hall must then be provided with a travelling crane which is dimensioned for the weight of the gas generator, and also requires that the station building be constructed with a much stronger framework than would otherwise be necessary.